1. Field of the Disclosure
This disclosure relates generally to oilfield downhole tools and more particularly to methods and devices for transferring rotary power to a consumer.
2. Description of the Related Art
Threaded connections are a prevalent method to join two or more members such as pipe sections. In certain applications, as during hydrocarbon exploration and recovery operations, a string of pipe sections joined by threaded connections may be rotated in a well bore. For example, a drill string may be rotated to urge a bottomhole assembly into a subterranean formation. The bottomhole assembly (BHA) also may include components that are mated or joined with threaded connections. In certain instances, drilling activity may cause the string and BHA to bend. As is known, the bending of threaded connection induces compression on one side of the threaded connection and a tension on the other side of the threaded connection. Because the threaded connection is rotating, the tension and compression is cyclical. It is, of course, also known that cyclical bending stresses imposed by even moderate loadings may lead to failure of the threaded connection (e.g., high cycle fatigue).
The harsh drilling conditions of the well bore environment or deviated well bores can cause such cyclical bending stresses in these threaded connections. Unfortunately, conventional threaded connections, such as those specified by the American Petroleum Institute (API), do not always possess sufficient bending fatigue resistance to support advanced drilling programs or complex well bore trajectories. For example, in some instances, drilling operations and hydrocarbon recovery may require a highly deviated well bore, e.g., a well bore having a sharp radius portion. Form deviated wellbore sections requires a BHA and drill string that can withstand a relatively high “build-up rate.” Conventional threaded connections subjected to such build-up rates can suffer reduced operational lifetime or require additional maintenance or rework. Moreover, even common drilling conditions slowly degrade conventional threaded connections such that these connections must be either changed-out or reworked. The costs incurred in such activity not only include the maintenance itself but, for example, the delay in drilling activities.
The present invention addresses these and other drawbacks of conventional threaded connections.